Cerebral palsy (CP) is the most common pediatric neurological disorder. CP is caused by damage to brain motor areas during development. CP results in weakness, altered tone and abnormal coordination. People with unilateral spastic cerebral palsy (USCP) tend to under-use their paretic side, and do not develop robust motor control of the paretic side. As people with USCP age, motor deficits on the paretic side persist due to disuse of the paretic side. Few therapies exist for upper extremity rehabilitation in adults with USCP. The goal of the present study was to determine feasibility and efficacy of upper limb therapy in adults with CP. Upper extremity robotic therapy can improve arm movement deficits in adults after stroke. Transcranial direct current stimulation (tDCS) can augment the efficacy of robotic therapy when delivered immediately before training. We propose to test this same protocol in USCP. We hypothesize that tDCS plus upper extremity robotic training will be a safe, feasible protocol that improved upper extremity function. Participants will receive thirty-six sessions of therapy, three days/week for 12 weeks. During each therapy session, each participant will receive 20 min of real 2mA anodal tDCS or sham tDCS, immediately followed by robotic arm therapy. Anodal (excitatory) tDCS will be applied over the motor map of the paretic hand. During robotic therapy, each participant will use the wrist and upper arm to follow a cursor in a center-out task for 1000 movements. We will measure motor function of the affected upper limb before, after, and six months after the series of therapy sessions. We will also measure kinematics of movements on the robot and side effects of tDCS at each session. We will also measure motor cortex excitability before and after the series of therapy sessions, using single pulse transcranial magnetic stimulation. We hypothesize that therapy will result in improved reaching accuracy and smoothness on the robotic task, improvement in clinical motor measures, and will show an excellent safety profile. We also hypothesize that the therapy will expand the motor map of the paretic hand. Understanding the feasibility, efficacy, and neurophysiological effects of combined tDCS and robotic therapy will be an important step in developing and optimizing effective upper limb therapy for adults with CP.